Conversion from rotation to linear motion, is mainly used in various occasions such as machine tools, motors and indexing mechanisms, and the most commonly used mechanisms for realizing this function include chains, steel wire ropes, driving belts, cams, pneumatics, hydraulics, racks or screw rods. Different mechanisms can be used for different occasions of conversion from rotation to linear motion, and they also have different advantages and disadvantages. For example, although the pinion and rack has advantages such as unlimited stroke, heavy load and convenient installation, there are also disadvantages such as backlash, large vibration in agglutination between teeth, large noise and difficulty in ensuring consistency of accuracy. Although belt drive has advantages of fast running speed, low noise and low cost, it has poor rigidity, easy wear and fatigue, low precision, small thrust, and etc. Although the screw rod has high precision, good rigidity and low noise, it has disadvantages such as short stroke, slow speed, difficulty in ensuring consistency of stroke accuracy, and etc.
Line gear is a new-type gear, which is mainly based on a space curve meshing theory. Different from the traditional meshing theory of surface contact or line contact, this theory is a pair of spatial conjugate curves realizing transmission gear by point meshing. The invention and research of the line gear have been developed for more than ten years. It has advantages such as small size, large transmission ratio and convenient manufacturing and it is mainly used in the field of micro transmission. For the research of the line gear, the current focus is mainly on transmission from rotation to rotation between two-inclined axes of a same plane, or in two staggered axes of different planes, while the line gear mechanism for conversion from rotation to linear motion has not yet begun to be involved into.